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Iron by Karen Schroeder Kassel, MS, RD, MEd

Functions

Iron's functions include:

In hemoglobin, carrying oxygen to cells throughout the body
In myoglobin, holding oxygen within the cells, especially heart and skeletal muscle cells
Forming collagen, which is the major protein that makes up connective tissue, cartilage, and bone
Helping fight infection by synthesizing certain enzymes needed for immune function
Helping convert beta carotene to vitamin A
Helping make amino acids, which are the building blocks of protein
Aiding drug detoxification pathways in the liver
Forming part of an enzyme that is essential for the production of several neurotransmitters
Synthesizing cellular components that are important to metabolism

Recommended Intake

Iron needs are greatest during times of rapid growth—childhood, adolescence, and pregnancy. Also, women have higher requirements than men, to replace the iron that is lost with monthly menstruation.

Age Group	Recommended Dietary Allowance (RDA) (mg/day)
Age Group	Male	Female
0-6 months	No RDA; Adequate Intake (AI) = 0.27	No RDA; Adequate Intake (AI) = 0.27
7-12 months	11	11
1-3 years	7	7
4-8 years	10	10
9-13 years	8	8
14-18 years	11	15
19-50 years	8	18
51+ years	8	8
Pregnancy	n/a	27
Lactation, equal to or less than 18 years	n/a	10
Lactation, 19-50 years	n/a	9

Iron Deficiency

Groups of people who are susceptible to being iron deficient are:

Women of childbearing years
Teenage girls
Female athletes
Infants (depending on their diet)
Children
Elderly
Low-income groups
People with Crohn’s disease or celiac disease—Iron is absorbed from a small intestine, and diseases affecting it may lead to poor absorption from food sources.

Iron-Deficiency Anemia

There are no symptoms of iron deficiency unless you become anemic. If not corrected, iron deficiency can progress to anemia. Symptoms of anemia include:

Fatigue: feeling tired all the time or getting tired easily with activities you used to be able to do without difficulty
Difficulty maintaining body temperature
Pale skin, especially the pink lining to your lower eyelids, under your fingernails, or your gums
Decreased immune function
Glossitis (an inflamed tongue)
Unusual cravings for substances like ice, dirt, etc. (called pica)

Iron-deficiency anemia is usually treated by increasing iron intake through dietary sources and iron supplementation.

Iron Toxicity

At high levels, iron is toxic. And since the body has no effective means of excreting excess iron, it is possible, although not very common, for iron to accumulate. Iron pills and supplements containing iron that are designed for adults can cause poisoning in children.

Symptoms of iron toxicity include:

Vomiting
Diarrhea (with or without blood)
Fever
Exhaustion

Major Food Sources

Food Sources of Mostly Heme Iron

Food	Serving size	Iron content (mg)
Chicken liver, cooked	3-½ ounces	12.8
Oysters, breaded and fried	6 pieces	4.5
Beef, chuck, lean only, braised	3 ounces	3.2
Clams, breaded, fried	¾ cup	3.0
Beef, tenderloin, roasted	3 ounces	3.0
Turkey, dark meat, roasted	3-½ ounces	2.3
Beef, eye of round, roasted	3 ounces	2.2
Turkey, light meat, roasted	3-½ ounces	1.6
Chicken, leg, meat only, roasted	3-½ ounces	1.3
Tuna, fresh bluefin, cooked, dry heat	3 ounces	1.1
Chicken, breast, roasted	3 ounces	1.1
Halibut, cooked, dry heat	3 ounces	0.9
Crab, blue crab, cooked, moist heat	3 ounces	0.8
Pork, loin, broiled	3 ounces	0.8
Tuna, white, canned in water	3 ounces	0.8
Shrimp, mixed species, cooked, moist heat	4 large	0.7

Food Sources of Nonheme Iron

Food	Serving size	Iron content (mg)
Ready-to-eat cereal, 100% iron fortified	¾ cup	18.0
Oatmeal, instant, fortified, prepared with water	1 cup	10.0
Soybeans, mature, boiled	1 cup	8.8
Lentils, boiled	1 cup	6.6
Beans, kidney, mature, boiled	1 cup	5.2
Beans, lima, large, mature, boiled	1 cup	4.5
Beans, navy, mature, boiled	1 cup	4.5
Ready-to-eat cereal, 25% iron fortified	¾ cup	4.5
Beans, black, mature, boiled	1 cup	3.6
Beans, pinto, mature, boiled	1 cup	3.6
Molasses, blackstrap	1 tablespoon	3.5
Tofu, raw, firm	½ cup	3.4
Spinach, boiled, drained	½ cup	3.2
Spinach, canned, drained solids	1 cup	2.5
Black-eyed peas (cowpeas), boiled	1 cup	1.8
Spinach, frozen, chopped, boiled	½ cup	1.9
Grits, white, enriched, quick, prepared with water	1 cup	1.5
Raisins, seedless, packed	½ cup	1.5
Whole wheat bread	1 slice	0.9

Other Health Implications Related to Iron

Hemochromatosis

People with the genetic disease hemochromatosis absorb excessive amounts of iron. This leads to a buildup of iron in the bloodstream and in certain organs, including the liver, muscles, pancreas, and heart. Signs and symptoms of disease usually do not appear until midlife. People of Northern European descent and men are at higher risk. Without treatment, high levels of iron can damage these organs. Treatment involves eating a diet low in iron and donating blood regularly.

Heart Disease and Cancer

Some research has suggested that excess levels of iron in the body may lead to an increased risk for heart disease or cancer. These effects may be due to how the body metabolizes iron, as opposed to how much iron is in the diet. However, the research in these areas is still inconclusive.

Tips for Increasing Your Iron Intake

The amount of iron your body absorbs varies depending on several factors. For example, your body will absorb more iron from foods when your iron stores are low and will absorb less when stores are sufficient.

In addition, certain dietary factors affect absorption:

Heme iron is absorbed more efficiently than nonheme iron.
Heme iron enhances the absorption of nonheme iron.
Vitamin C enhances the absorption of nonheme iron.
Some substances decrease the absorption of nonheme iron:
- Oxalic acid, found in spinach and chocolate (However, oxalic acid is broken down with cooking.)
- Phytic acid, found in wheat bran and beans (legumes)
- Tannins, found in tea
- Polyphenols, found in coffee
Note: Consuming heme iron and/or vitamin C with nonheme can help compensate for these decreases.

To increase your intake and absorption of dietary iron, try the following:

Combine heme and nonheme sources of iron.
Eat foods rich in vitamin C with nonheme iron sources. Good sources of vitamin C include:
- Bell peppers
- Papayas
- Oranges and orange juice
- Broccoli
- Strawberries
- Grapefruit
- Cantaloupe
- Tomatoes and tomato juice
- Potatoes
- Cabbage
- Spinach and collard greens
If you drink coffee or tea, do so between meals rather than with a meal.
Cook acidic foods in cast iron pots. This can increase iron content up to 30 times.

RESOURCES:

Academy of Nutrition and Dietetics http://www.eatright.org
Vegetarian Resource Group http://www.vrg.org/

CANADIAN RESOURCES:

Health Canada Food and Nutrition http://www.hc-sc.gc.ca/fn-an/index-eng.php
Dietitians of Canada http://www.dietitians.ca/

References:

Centers for Disease Control and Prevention. Recommendations to prevent and control iron deficiency in the United States. Morbidity and Mortality Weekly Report. 1998;47:1-32. Available at: http://wonder.cdc.gov/wonder/PrevGuid/m0051880/m0051880.asp .
Duyff R. The American Dietetic Association's Complete Nutrition Guide . Chronimed Publishing; 1998.
Dietary supplement fact sheet: iron. Office of Dietary Supplements website. Available at: http://ods.od.nih.gov/factsheets/iron.asp. Accessed August 1, 2012.
Pennington J. Bowes & Church's Food Values of Portions Commonly Used . 17th ed. Lippincott Williams & Wilkins; 1998.
Wardlaw G, Insel P. Perspectives in Nutrition . 2nd ed. Mosby Year Book, Inc.; 1993.

Last reviewed August 2012 by Brian Randall, MD

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